[longevity] rebalance does not fail when 2 nodes down during rebalance

Cluster information:

• Load 9 million items to both buckets
• Cluster has 2 buckets, default (3GB) and saslbucket (3GB)
• Each bucket has one doc and 2 views for each doc (default d1 and saslbucket d11)

• Create cluster with 10 nodes installed couchbase server 2.0.0-1708

10.3.121.13
10.3.121.14
10.3.121.15
10.3.121.16
10.3.121.17
10.3.121.20
10.3.121.22
10.3.121.24
10.3.121.25
10.3.121.23

• Data path /data
• View path /data

• Failover node 13
• Add back node 13 and remove node 25
• During rebalance, kill beam.smp on node 14 and 24 (kill -s SIGUSR1 pid).
• Rebalance did not fail but hang

Link to diags of 10 nodes https://s3.amazonaws.com/packages.couchbase/diag-logs/orange/201209/10nodes-1708-reb-not-failed-when-node14-24-down-20120911-204502.tgz